Syntheses and structures of TcOF5 and the Tc2O2F9+ cation and formation ofthe TcOF4+ cation in solution

The last member of the series of technetium(VII) oxide fluorides, TcOF5, ha s been prepared by oxidative fluorination of TcO2F3 with KrF2 in anhydrous HF. The pseudooctahedral (C-4v) structure Of TcOF5 has been determined by F -19 and Tc-99 NMR, Raman, and infrared spectroscopies and by single-crystal X-ray diffraction. TcOF5 crystallizes in the orthorhombic crystal system, space group Pna2(1), with a = 9.235(3) Angstrom, b = 4.939(2) Angstrom, c = 8.502(3) Angstrom, V = 387.7(2) Angstrom(3), and Z = 4 at -102 degrees C, R-1 = 0.0256 and wR(2) = 0.0730. TcOF5 behaves as a fluoride ion donor towa rd AsF5 and SbF5 in HF solvent, giving the Tc2O2F9+ cation, which has been characterized as the AsF6- and Sb2F11- salts by Raman spectroscopy and as t he [Tc2O2F9][Sb2F11] Salt by single-crystal X-ray diffraction. [Tc2O2F9][Sb 2F11] crystallizes in the orthorhombic crystal system, space group Pbcm, wi th a = 6.2925(4) Angstrom, b = 21.205(2) Angstrom, c = 11.7040(8) Angstrom, V = 1561.7(2) Angstrom(3), and Z = 8 at -90 degrees C, R-1 = 0.0368 and wR (2) = 0.0896. The Tc2O2F9+ cation consists of two fluorine-bridged square p yramidal TcOF4 groups in which the fluorine bridge is trans to the oxygens. Solution F-19 and Tc-99 NMR spectra of Tc2O2F9+ salts in HF and of TcOF5 d issolved in SbF5 are consistent with the formation of the TcOF4+ cation. Lo cal density functional theory has been used to calculate the geometrical pa rameters, vibrational frequencies, and F-19 and Tc-99 NMR parameters of MOF 5 (M = Tc, Re, Os) and TC2O2F9+, which are in good agreement with available experimental values. The results of ab initio calculations and normal coor dinate analyses for MOF5 confirm the trans influence of oxygen, which leads to lengthening of the axial fluorine-metal bond length and a corresponding ly lower stretching force constant relative to that of the shorter equatori al metal-fluorine bonds.